The phosphoric acid is one of the important chemical materials. The processes for preparing phosphoric acid are classified as wet-process and heat-process. Typical wet-process for preparing phosphoric acid is comprising: decomposing phosphate rock with sulfuric acid and separating the resulted phosphate rock slurry into phosphoric acid and calcium sulfate. In accordance with condition and the number of crystalline water in produced calcium sulfate, the wet-processes are classified as dihydrate, hemihydrate, anhydrous, hemi-dihydrate and di-hemihadrate process. Among them, the anhydrous process can't be industrialized by now, and hemihydrate process is used seldom because of its severe operation. Now, the dihydrate process is the main one for preparing phosphoric acid. The production by such process is up to 80% or more of total production of phosphoric acid, and the scale of its apparatus becomes larger and larger. However, dihydrate process has two shortages: one is the co-crystallation of CaHPO4 in the gypsum crystal lattice, and thereby the loss of P2O5 is high and recovery efficiency is low; the other is that the concentration of phosphoric acid is low and only about 30%. Now in China, the dihydrate process is dominant, and hemihydrate or hemi-dihydrate process takes second place, and di-hemihadrate process has not been reported.